Spreading of P301S Aggregated Tau Investigated in Organotypic Mouse Brain Slice Cultures

Abstract

Tau pathology extends throughout the brain in a prion-like fashion through connected brain regions. However, the details of the underlying mechanisms are incompletely understood. The present study aims to examine the spreading of P301S aggregated tau, a mutation that is implicated in tauopathies, using organotypic slice cultures. Coronal hippocampal organotypic brain slices (170 µm) were prepared from postnatal (day 8–10) C57BL6 wild-type mice. Collagen hydrogels loaded with P301S aggregated tau were applied to slices and the spread of tau was assessed by immunohistochemistry after 8 weeks in culture. Collagen hydrogels prove to be an effective protein delivery system subject to natural degradation in 14 days and they release tau proteins up to 8 weeks. Slices with un- and hyperphosphorylated P301S aggregated tau demonstrate significant spreading to the ventral parts of the hippocampal slices compared to empty collagen hydrogels after 8 weeks. Moreover, the spread of P301S aggregated tau occurs in a time-dependent manner, which was interrupted when the neuroanatomical pathways are lesioned. We illustrate that the spreading of tau can be investigated in organotypic slice cultures using collagen hydrogels to achieve a localized application and slow release of tau proteins. P301S aggregated tau significantly spreads to the ventral areas of the slices, suggesting that the disease-relevant aggregated tau form possesses spreading potential. Thus, the results offer a novel experimental approach to investigate tau pathology.

A Combination of Heavy Metals and Intracellular Pathway Modulators Induces Alzheimer Disease-like Pathologies in Organotypic Brain Slices

“…Tau5+ cells and fiber density increased in WT and TG APP_SDI slices with P301S aggTau-loaded hydrogels compared to control slices. This aligns with the hypothesis that exogenous tau aggregates boost tau+ immunoreactivity, consistent with previous findings of increased tau+ immunoreactivity in the ventral parts of slices from WT postnatal mice [15]. The presence of hAβ42 does not impact tau accumulation in WT slices, as evidenced by the lack of a significant difference in immunoreactivity between slices incubated with hAβ42 and P301S aggTau versus P301S aggTau alone.…”

“…This contrasts with previous reports of no tau pathology in this mouse model [4]. The outcome resonates with the prior observations using postnatal slices treated with P301S aggTau-loaded collagen hydrogels [15]. In adult slices, hAβ42-loaded collagen hydrogels led to a significant increase in AT8+ immunoreactivity, indicating differential responses in aged/mature neurons to exogenous hAβ42.…”

“…The use of nanomolar concentrations ensures minimal impact on cellular viability. Lastly, culturing slices from postnatal mice for over 2 months allows exploration of the spreading of amyloid and tau pathology, as demonstrated in previous studies from our lab [15,18,19].…”

“…Cells and synapses develop in a manner comparable to the in vivo environment [14]. This system allows direct and repeated manipulation, including the addition of exogenous compounds to the medium or application of collagen hydrogels to achieve a slow, localized protein or peptide release [15][16][17][18][19]. The absence of a blood-brain barrier permits direct investigation of the effects of toxic or therapeutic compounds [20].…”

“…Slice cultures have been used to study this pathology transmission [16,17]. Our prior research on postnatal WT animals showed increased spreading of P301S aggregated tau (aggTau) to the ventral areas of slices via neuroanatomically connected pathways [15]. Sagittal slices from a TG mouse model of Parkinson's disease overexpressing α-synuclein exhibited enhanced spreading of α-synuclein pre-formed fibrils compared to WT mice [19].…”